An example of a service, in which one of several modes may be used, would be a positioning system. The positioning system allows the determination of the position of a receiver of the positioning system by processing signals transmitted by beacons of the positioning system. This receiver may, for example, be used in a mode with reduced power consumption, which could also be a mode in which it is turned off completely, or in a fully operational mode.
There is an ever increasing number of devices using such a positioning system in order to determine their absolute position. Most often this is achieved by making use of a Global Navigation Satellite System (GNSS), of which the American global positioning system (GPS) and the European Galileo are but two examples. These systems enable a receiver to determine its position by just utilizing the downlink data sent by the respective set of satellites. There are also terrestrial localization techniques like cell identification and time difference of arrival (TDOA) that may be used for positioning which use only beacons on the ground rather than in space.
Problematic signal reception conditions in some urban environments, among other things, have led to the development of assisted GNSS (A-GNSS) technology for improving the performance of GNSS when signal quality is not optimal. A variety of approaches, which are characterized by the use of an assistance server, is subsumed under this category. An assistance server may have a better reception of signals and/or more computation power and additional information useful for positioning.
While originally the kind of devices having a GNSS receiver was limited, advances in miniaturization make it possible to use GNSS receivers in ever smaller and lighter devices. One exemplary kind of device to which this applies is the mobile phone. The positioning capability in mobile phones is most typically enabled by the use of either external or internal receivers. Moreover, the inherent communication capabilities of mobile phones enable a data exchange between the receiver and an assistance server
The penetration of GNSS or A-GNSS enabled terminals is expected to increase significantly in the coming years. In 2011 it is estimated that approximately 30% of the terminals sold will have an internal AGNSS receiver. But it is not only positioning capability that is steadily added to mobile terminals. More and more functionality that was originally restricted to stationary computer systems is now a part of an increasing variety of mobile devices. This includes the ability to run platform-independent software like Java®, play back multimedia files and also connect to traditional computer systems and media with technology like universal serial bus (USB), Bluetooth® and wireless local area network (WLAN). Mobile phones, vehicle infotainment systems, personal digital assistants (PDAs) and mobile game consoles form an increasing variety of devices which all converge in their respective capabilities toward a mobile general-purpose computer. This trend towards multi-use terminals consisting of multiple processors, advanced camera and video features, multiple connectivity methods as well as navigation capability results in an ever increasing power consumption.
Also in the case of cellular based localization techniques, for which the device in question does not have to be a mobile phone in the strict sense but does have mobile communication capabilities nonetheless, such as a wrist watch with emergency mobile communications functionality, size and energy constraints may make it seem advantageous to have only intermittent connectivity to a cellular network.
Inertial sensors (or the consideration of the velocity solution, which is of less practical relevance in this context) can be used for detecting a motion of a device. If the inertial sensor detects that the mobile device is in fact stationary, then there is no need to continuously recalculate the current position based on the received signals. Consequently the positioning system receiver may be switched off or at least its power consumption decreased by reducing its measurement rate or a similar measure. Moreover, a more accurate position solution may be obtained if information on the state of motion of the receiver is available. If the receiver is known to be stationary, for example, a plurality of determined positions may be averaged.
It is to be understood that a switch between different available service modes may also be relevant to other types of services than positioning, and that service modes also do not necessarily relate to power consumption.